The developing trends of Isolated Bidirectional Direct Current-Direct Current (DC-DC) Converters (IBDC) are Wide Input-Wide Output (WIWO) voltage for very high efficiency, high power density and low cost. The resonant DC-DC converters are suitable technology to achieve high efficiency due to its intrinsic feature to achieve soft switching (Zero Voltage Switching, ZVS, and Zero Current Switching, ZCS). Furthermore, it is possible in these circuits to increase the switching frequency in order to reduce the size of the reactive components.
Common and widely used bidirectional DC-DC converters found in the industry today are the Dual Active Bridge (DAB) and resonant converters due to their availability to achieve high efficiency.
However, there are still remaining drawbacks regarding the conventional resonant converters at bidirectional operation (i.e. forward- and reverse-mode), e.g. mainly the voltage gain characteristic at reverse mode of operation. Furthermore, the high AC-current at the low voltage side of the output filter resulting in high power losses and large volume of the filter if the current technology is going to be used.
With the described bidirectional topological circuits according to conventional solutions the current stress on the resonant components on the low voltage side is high and compromises the efficiency of the converter.
Also, with the described bidirectional topological circuits according to conventional solutions it is not possible to achieve WIWO voltage and high efficiency. Moreover, it is very hard to get new topological circuits with reduced number of the active components (controlled semiconductors) where high reliability and performance in bidirectional energy conversion systems are required.